1. Field of the Invention
The present invention relates to an apparatus and method for sterilizing food and, more particularly to the sterilization of the food in the apparatus which includes a sterilizing chamber for heating and sterilizing the food and a cooling chamber continuously connected to the sterilizing chamber.
2. Description of the Related Art
Various types of sterilizing apparatus wherein food is successively advanced into a sterilizing chamber for heating and sterilizing food at high temperature (or at high temperature and under high pressure) are known. For example, see Japanese Patent Laid-Open Publication No. 49-71177, Japanese Patent Laid-Open Publication No,. 51-42391 and Japanese Patent Laid-Open Publication No. 64-51069.
With any of these sterilizing apparatuses, conveying means for advancing the food must be arranged within the sterilizing chamber of the apparatus. However, the conveying means provided within the sealed sterilizing chamber can make the entire configuration of the apertures complex or complicated and is disadvantageous to maintaining the sterilizing chamber in aseptic condition.
In an attempt to resolve such problems explained above, different food sterilizing apparatuses have been proposed to successively advance the food in a sealed and heated sterilizing chamber without the conveying means provided within the sterilizing chamber, for example, in co-pending U.S. patent application Ser. No. 08/395,111 filed on Feb. 27, 1995, assigned to the assignee of the present application. In the suggested apparatus, food received in containers is heated and sterilized in a heater (heating and sterilizing chamber) and then, successively advanced into a cooler (cooling chamber) connected to the heater via a sealing gate and cooled. The sealing gate provided between the heater and cooler is intermittently opened, so that the containers are advanced from the heater to the cooler. In this apparatus, the inner pressure of the heater is set at a level higher than that of the cooler in order to prevent the inflow of the cooled air into the heater during opening of the sealing gate.
However, with the above arrangement, due to the higher pressure in the heater, a rapid pressure drop occurs on the heater side of the sealing gate when the sealing gate is opened. The pressure drop causes the re-boiling phenomenon, that is, the drain water in the heater bumps and wets the food. The bumping water significantly deteriorates the quality of the food.